Gasifiable casting pattern



April 18, 1967 A. WITTMOSER ETAL 3,314,116

GASIFIABLE CASTING PATTERN Filed July 30. 1963 5 Sheetsheet l INVENTORS.

Adolbert Wiflmoser Johannes Schode Erich Krzyzonowski by Ronutd E.BurryAttorney April 13, 1 A. WITTMOSER ETAL 3,314,116

GAS IFIABLE CASTING PATTERN Filed July 30. 1963 i 5 Sheets-Sheet 2 Fl G.5 I

73G 73d 73 730 (3b FIG.7

' INVENTORS Adolberf Wmmoser Johannes Schode Erich Krzyzqflowski byRonald E. Barry Attorney April 18, 1957 A. WITTMOSER ETAL 3,

I GASIFIABLE CASTING PATTERN Filed July so, 1963 s Sheetsheet 5 FIG.8

INVENTORS Adulbert Wiflmoser Johannes Schode I Erich Krzyzonowski byRonald E. Barry Attorney United States Patent This application is acontinuationin-part of our copending application Ser. No. 270,085, filedApr. 2, 1963, and entitled, Casting Arrangement and Method.

The present invention relates to a casting arrangement,

and more particularly, the present invention is concerned withimprovements relating to gasifiable patterns.

According to conventional casting procedures a pattern having the shapeof the casting to be made and consisting of wood-metal, wax, syntheticresin, etc., is embedded in an appropriate molding material or moldingsand respectively, inthe mold. After packing the molding material toform a mold body, the pattern is removed and the melt is poured into thecavity which remains in the molding material. For this procedure lostpatterns can be applied that means patterns which are destroyed afterembedding, for example when employing a wax pattern which is melted out.

A considerably simplified casting procedure is suggested in U.S. PatentNo. 2,830,343. According to this method the pattern is made of expandedplastic such as polystyrene or a similar material, remains afterembedding in the mold, and is gasified and decomposed practicallywithout residue by the penetrating melt. A dry, noncaking moldingmaterial may be used according to this method to which, however, a coldsetting binder is added for reasons of expediency.

However, tests have shown, that the quality of castings producedaccording to this molding procedure frequently do not come up to theexpectations, as undesirable reactions may, and frequently do, occurbetween the molten casting charge and products formed in thegasification of the plastic pattern material and/or reactions of themelt or molten charge with the molding material. These difficulties areparticularly serious in case a dry, noncaking molding material is used,as the resistance of such molding material to the eroding effect of thepenetrating melt is not sufficient. By incorporating a binder in theloose molding material its resistance can be increased, but at the sametime the permeability of the molding material to the gases formed of thecellular plastic pattern is considerably decreased and furthermore otherdisadvantages of such binding agents such as high price and unpleasantodor will be encountered.

It is therefore an object of the present invention to overcome the abovediscussed disadvantages.

It is another object of the present invention to improve the usefulnessof gasifiable casting patterns.

It is a further object of the present invention to provide improvedgasifiable casting patterns which can be produced and used in a simpleand economical manner.

It is a further object of the present invention to provide castingarrangements including improved feeder head patterns.

Other objects and advantages of the present invention willbecorneapparent from a further reading of the description of the appendedclaims.

With the above and other objects in view, the present inventioncontemplates in a casting arrangement, in combination, a moldingmaterial having embedded therein a body consisting essentially of agasifiable member having substantially the configuration of an articleto be cast and adapted to be gasified at an elevated temperaturecorresponding to the temperature of "a molten casting charge adapted tobe cast to form the article, and a layer consisting of a solid materialwhich remains solid at the elevated temperature, contacting andsubstantially completely covering the outer surface of the gasifiablemember.

According to a preferred embodiment, the present invention contemplatesfor use in a casting arrangement, a casting pattern, comprising, incombination, a gasifiable body having substantially the configuration ofan article to be cast and being adapted to be gasified at an elevatedtemperature corresponding to the temperature of a molten casting chargeadapted to be cast to form the article the gasifiable body havingdistributed therethrough a substance adapted to act on the moltencasting charge, and a layer consisting of a solid material which remainssolid and is gas permeable at the elevated temperature, contacting andsubstantially completely covering the outer surface of the gasifiablebody and having incorporated therein a substance adapted upon contactwith the casting charge to affect the surface properties of the castarticle.

The present invention also includes a method of casting, comprising thesteps of embedding in a mold body a form which is gasifiablesubstantially without residue on subjection to a molten casting chargeand which is shaped for exact reproduction as a casting and the surfaceof which is covered with a layer consisting of a solid material whichremains solid and is gas permeable at the temperature of the moltencasting charge, providing in the mold body and in the layer a passagefor a molten casting charge to the embedded form, and pouring into thepassage a molten casting charge for gasifying and replacing the embeddedform in the mold body.

The present invention is also concerned with patterns which consistessentially of combustible or gasifiable substances such as expandedplastics and the like, which patterns are particularly suitable asfeeder heads of the type which are frequently incorporated in castingarrangements in order to prevent formation of shrinkage cavities duringcasting of the molten metal. The feeder head patterns according to thepresent invention have been found to give very good results inconnection with the process of casting which is described in US. PatentNo. 2,830,343.

Thus, the present invention also contemplates in a casting arrangement,in combination, a casting pattern consisting'essentially of a gasifiablemember having substantially the configuration of an article to be castand consisting essentially of a material adapted to be gasified at anelevated temperature corresponding to the temperature of a moltencasting charge adapted to be cast to form the article, a feeder headpattern of substantially spherical configuration and consistingessentially of a material adapted to be gasified at the elevatedtemperature operatively connected to the casting pattern, and a body ofmolding material enveloping and having embedded therein the castingpattern and the substantially spherical gasifiable feeder head.

Thus, the present invention utilizes a gasifiable casting pattern ofexpanding plastic, for instance of polystyrene or polyethylene and isconcerned with an improvement of the casting method which is disclosedin US. Patent No. 2,830,343, according to which the gasifiable castingpattern is embedded in a molding material, for instance, a molding sandor other loose, non-shaping material to which a cold setting binder maybe added, and whereby the pattern is gasified and decomposed by the heatof the penetrating melt or molten casting charge.

According to the present invention, the outer surface of the pattern isprovided with a shell-like, substantially incombustible coat or layerwhich will not be affected by the temperature of the penetrating meltand which preferably will be highly permeable to gas or becomingpermeable to gas during the pouring process. It is also within the scopeof the present invention to incorporate in the cellular plastic castingpattern solid or gaseous materials which will act on, or react with, themolten casting charge, for instance in the case of a molten metalcasting charge, a material which will cause a metallurgical treatment ofthe casting metal.

The present invention thus overcomes the difficulties experienced up tonow in connection with gasifiable casting patterns and will result inthe production of cast bodies or castings of the desired surfacestructure, even when embedded in a loose molding material such as dryquartz sand which need not contain any binder. Even metal shot orsimilar materials may be used as the molding material. Furthermore,according to the present invention, not only an improvement of thesurface of the casting is achieved but also of its inner structure whichmay be influenced by the incorporation of suitable materials in thegasifiable cellular plastic casting pattern.

The shell-like, substantially incombustible coat or layer on the outerface of the cellular plastic pattern will also advantageously act as abarrier preventing the escape of alloying and similar materials whichmay have been incorporated in the cellular gasifiable plastic castingpattern. In other words, when upon contact with the molten castingcharge the expanded or foam cellular plastic pattern is burned out ordecomposed and in any event gasified and the thus formed gases passoutwardly through the porous incombustible layer surrounding thecellular plastic pattern and separating the same from the moldingmaterial, the surrounding in'combustible layer may be such as to preventpassage therethrough of alloying or other materials which had beendistributed throughout the gasifiable plastic pattern. The porous layerthus may be traversed by the gases formed, for instance, by pyrolysis ofthe cellular plastic but will retain and prevent passage therethrough ofthe particles of the alloying or the like material in the mold, whichparticles of alloying or the like material will thus be incorporated in,or react with, the casting charge.

The novel features which are considered as character istic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIG. 1 is a perspective view of a gasifiable casting pattern accordingto the present invention;

FIG. 2 is a cross sectional view taken along lines II-II of FIG. 1;

FIG. 3 is an elevational view partially in cross section of a castingpattern for a radiator, according to the present invention;

FIG. 4 is a cross sectional view taken along lines -IV-IV of FIG. 3;

FIG. 5 is an elevational cross sectional view of a casting moldincorporating the casting pattern of FIGS. 1 and 2;

FIGS. 6-10 will serve primarily to illustrate embodiments of the presentinvention which encompass a gasifiable feeder head;

FIG. 6 is an elevational view in cross section of a molding box withembedded feeder head and casting pattern;

FIG. 7 is a cross sectional view taken along line A-A of FIG. 6;

FIG. 8 is an elevational, cross sectional view of another embodiment ofthe present invention;

FIG. 9 is a fragmentary, elevational, cross sectional view of a furtherembodiment of the present invention; and

FIG. 10 is a fragmentary, elevational, cross sectional view of yetanother embodiment of the present invention.

The casting pattern 1 which is illustrated in FIGS. 1, 2 and 5 may serveas an example for producing a casting in accordance with the presentinvention without requiring a core, while at the same time providing thecasting with hardened surface portions in the area of the wheel body.Furthermore, as illustrated in FIG. 5, the casting will be produced inaccordance with the present invention so as to be substantially free ofcavities and pipings.

Tthe upwardly extending portions 2, as shown in FIG. 1, serve forreliable attachment of the risers and feeding conduits shown in FIG. 5.

As illustrated in FIG. 2, the gasifiable foamed plastic pattern 1carries a porous layer or coat 3 which covers the entire outer surfaceof plastic pattern 1. Incorporated and substantially evenly distributedthroughout foam cellular plastic pattern 1 may be alloying materials orother materials which will act on the molten casting charge when thesame is introduced into the mold so as to gasify and replace the plasticpattern. Interposed between the layer 3 of solid material, which remainssolid at the temperature of the molten casting charge and whichpreferably will be gas permeable at such temperature, and thegasifia'ble member 1 may be a layer 4 of a material adapted to act onand to influence the surface portion of the casting during formation ofthe same, for instance to increase the hardness of the surface portion.

:FIGS. 3 and 4 illustrate one of the relatively rare cases when byproceeding in accordance with the present invention it is neverthelessdesirable to use a core.

As illustrated, the outermost layer 31 as shown in FIGS. 3 and 4,consists of a solid material which will remain solid at castingtemperatures and layer 31 contacts the outer surface of the gasifiablecellular plastic pattern 32. The core consists of a cellular plasticbody 33 and a layer 34 interposed between cellular plastic core 33 andcellular plastic pattern 32. Layer 34 consists of a material of low heatconductivity so that upon introduction of the molten casting charge andreplacement of gasifiable plastic pattern 32 by the casting charge, heatpenetration toward the gasifiable cellular plastic core portions 33 willbe considerably retarded, namely for a sutficient length of time so thatgasification of plastic core bodies 33 will take place only after theportion of the casting charge adjacent to layer 34'l1as been solidifiedand has become shape-retaining and self-supporting. Such corescontaining a gasifiable body are particularly suitable for castingswhich include relatively thin walls and which are formed with one ormore inner cavities access to which is relatively difiicult.

FIG. 5 illustrates the casting pattern of FIGS. 1 and 2 incorporated ina molding arrangement which includes a shell 51, mold body 52, openfeeder funnel 53 and feeder 54 with riser 55. Feeding funnel 53, feeder54 and riser 55 consist, initially similarly to pattern 1, of gasifiablecellular plastic material and feeding funnel 53 and feeder 54 aresurrounded by a layer of heat insulating material 56. The foamedcellular gasifiable plastic pattern again may have incorporated thereinsuitable alloying or treating materials for acting on or reacting withthe casting charge. Heat insulating layers 56 may consist of the porousgas permeable solid material which remains solid at casting temperaturesas described further above. The spherical blind riser 57 which is alsosurrounded by heat insulating layer 56 is formed with a small cutout atits upper portion which will serve for maintaining the elevatedtemperature of the melt for somewhat longer period of time. Theconstriction underneath spherical riser 57 will facilitate breaking offthe material which has solidified in riser 57.

It will be understood by those skilled in the art that many variationsof these auxiliary devices are possible and are within the scope of thepresent invention. Feeder and riser arrangements which are surrounded byheating means, usually providing heat by an alumin'o-thermic or the likeprocess, or by insulating materials have been known for a long time.However, up to now these elements had to consist of pressure resistant,hard, ceramic hollow bodies which had a relatively limited heating orinsulating effect and were quite expensively, while, according to thepresent invention, these members will consist of a form of gasifiablecellular plastic material which is covered with a layer of suitableinsulating material or the like.

Thus, in accordance with the present invention, by preforming feeders,risers and the like of gasifiable cellular plastic materials, which maybe joined to the casting pattern of the same type of materials, it ispossible to utilize layers of insulating materials which are highlyinsulating and relatively inexpensive although affording less pressureresistance, such as layers of mineral wool, and the like.

The materials which may be used for forming the solid gas permeablelayer 3 and which also may be used [for forming the heat insulatinglayer 56, are conventional materials which are, per se, known in theart. Heat resistant materials which are porous or which will becomehighly permeable to gas when exposed to the temperature of the moltencasting charge are highly suitable for the first purpose. Thesematerials include diatomaceous earth or kieselguhr, asbestos, syntheticmineral fibers such as mineral wool, fire clay, clay, pumice, bentonite,perlite, vermiculite and the like, to which quartz sand or a similarmaterial may be added if desired. As binding agents for these mineralmaterials may be used thermosetting or preferably cold settingsubstances such as plaster of Paris, cement, starch or synthetic resins,the latter being preferred. In a most simple manner, the layer is formedby preparing a suspension of the mineral material and binding agent inwater, to which suspension a suitable wetting agent and/or film formingagent may be added and which is then applied to the cellular plasticpattern, for instance, by hand, spray gun, immersion or other methods.The coating or layer will require only a short period of air drying, butit need not be subjected to a special drying process and may be allowedto stand in wet condition. The thickness of the coating preferably willnot exceed 6 mm. and more preferably will be between 2 and 5 mm. Theoutside of the layer or coating may remain in rough and unevencondition. It is a further advantage of the above-described coating thatit is possible to incorporate therein without diificulty materialswhich, when coming in contact with the casting charge, will affect thesurface properties of the casting. Moreover, it is possible to form alayer of a material which will favorably affect the properties of thecasting between the cellular pattern and the heat-resistant coating.Such layer, for instance, may be applied to the surface of the cellularplastic pattern prior to forming the heat resistant layer thereon.

In the production of castings which are required to have particularlyhard, wear-resistant surface portions, such as rollers and cam shaifts,such treating layer or coating may consist of graphite, tellurium orferrosilicon, in other cases, particularly when producing light metalcastings, a treating layer of silicon or sulfur frequently will be foundadvantageous for improvement of the surface quality of the casting.

The specific material of which the heat resistant gas permeable layer isto be formed will depend on the type of casting which is to be produced,such as whether an aluminum casting is to be produced at about 700 C. ora steel casting at about 1,500 C.

'For instance, in case of a casting to be formed of a metal having ahigh melting point, the heat resistant porous layer may be formed of amixture of about 85% by weight of unblown perlite, about 5% of waterglass (aqueous solution containing 30% by weight of sodium silicate) asbinder and about 10% by weight of ground graphite.

Water which may contain a wetting agent and a filmforming agent is addedin an amount sufficient to form a stiif paste which may be easilyapplied to the cellular casting pattern by hand and which dries quicklyand adheres well to the surface of the cellular plastic pattern. When itis desired to apply the layer 'by dipping or spraying, then a greaterquantity of water is added so as to achieve the desired consistencywhich is best suitable for the respective manner of applying the paste.

The perlite in the above-described mixture may be replaced by similarproportions of mineral wool, kieselguhr, ground pumice and the like.

The water glass binder may be replaced by a starch solution or asuitable solution or dispersion of synthetic resin.

The graphite may be suitably replaced by ferro-silicon or silicon.

The materials which may be incorporated in the heat resistant layer orwhich may be interposed between the heat resistant layer and the surfaceof the cellular plastic pattern, may either be mixed into the mass ofwhich the heat resistant layer is formed, or may be applied as anintermediate coating, for instance dispersed in alcohol or watercontaining a wetting agent and/or film forming agent.

As has been described above, it is possible according to the presentinvention to introduce into the casting charge while the same is fillingthe space originally occupied by the cellular plastic pattern, at leastone additional material which will serve to influence metallurgicallythe material of the cast workpiece. This is done by employing thecellular plastic material as the carrier for introducing such material.

The material which is intended to have a metallurgic effect on the meltor casting charge, or to alloy with the same, may be distributed asevenly as possible in the plastic material prior to blowing of the same,so that as a result of the expansion of the plastic material, an evendistribution of the added materials will be accomplished in the cellulargasifiable plastic pattern.

The gasifiable expanded plastic material which contains the evenlydistributed additional material may also be used to form the pouringsystem of the mold. Thus, for example, to influence the graphiteformation in castiron alloys, materials such as ferrosilicon or nodulargraphite-forming elements such as magnesium and corium may be added.Powdery substances may also be added to the expanded plastic for eitherpreventing or promoting the solidification of cast-iron alloys in theform of white cast iron, for example magnesium and silicon (preventives)or sulfur and tellurium (promoters).

Furthermore, alloying constituents, such as vanadium, molybdenum and thelike may be introduced into the melt in accordance with the presentinvention.

Such alloying materials, or other materials which serve to influence thequality of the casting formed of the molten casting charge, are usuallyadded. in such quantities that, with reference to the weight of thecasting, the alloying metals are present in an amount of up to 1%,silicon in an amount of up to 0.8% and magnesium in an amount of up to0. 1%. In order to incorporate such proportions of added material in thecasting, when employing the gasifiable expanded plastic pattern ascarrier, the expanded plastic may contain up to 500% of its weight ofalloying metal or silicon, or up to about 50% of its weight ofmagnesium, based on the weight of the expanded plastic.

In order to achieve a uniform distribution of such added alloying orother material in the expanded plastic, the additional material may beincorporated in the preexpanded granulate or in the monomers 01f theplastic. In the latter case, the added material may be distributedhomogeneously, prior to the polymerization, in one or more of themonomers prior to their admixture, or in the monomer mixture. The addedmaterial should be introduced in finely sub-divided form. This lastprocedure is particularly advantageous because it will result in a veryeven distribution of the added material, for instance an alloyingconstituent, in the expanded plastic.

If, in customary manner, the expansion of the plastic polymer will becarried out with the help of a suitable expanding agent under theinfluence of the super-heated steam, then certain difiiculties areencountered when the added material, for example magnesium in powderform, is attacked by water. If, on the other hand, the added material isintroduced into the monomeric resin, then the material which issensitive to steam will be distributed very homogeneously in plasticexpanded with the use of steam and apparently remains protected againstattack by Water due to the plastic material surrounding each of theparticles of magnesium or the like.

Rerferring now to the heat barrier or layer of low thermal conductivity,such as layer 34 of FIGS. 3 and 4, very good results are obtained in thecase of aluminum castings with layers formed of one part by weight of apolyvinylpropionate resin dispersion containing about 50% by weight ofresin and 50% by Weight of water, two parts by weight of lithopone, twoparts by weight of white cement and three parts by weight of water withthe addition of a small amount of a wetting agent.

The thickness of the thus formed dry layer of low thermal conductivitypreferably will be about 23 mm. and its weight about 300 grams persquare meter. However, these quantitative data should not be consideredas limiting the invention since innumerable variations may be made forspecific purposes. For instance, a metal powder or metal flakes and thelike may be incorporated in the layer, depending on the castingtemperature. The heat insulating layer 56 which primarily covers thecellular plastic material which is located in place of the riser andfeeder conduits, preferably will consist of a material of the type whichis suitable for forming layers 3 or 31, and very good results areachieved with respect to forming such porous layer by using thereformineral wool and a smoothening and binding agent such as bentonite.However, layers 56 preferably will be considerably thicker than layerssuch as layers 3 and 31.

The casting method of the present invention is not limited to anyspecific casting charge or material. It is possible to cast according tothe present invention substantially all casting metals such as bronze,light metals, iron, steel, heavy metals, as well as glass and silicatemelts (quartz), molten A1 SiC and the like. It is of course requiredthat the melt will be sufficiently fluid within a temperature rangewhich will be sufficiently above the decomposition or gasificationtemperature of the foam plastic pattern, and the last conditiongenerally is met by a temperature of about 400 C. Furthermore, it is ofcourse desirable that there should be as little reaction as possiblebetween the molten charge and the porous heat resistant layer or thelayer of low heat conductivity which covers the plastic pattern.

The plastic pattern according to the present invention, with the porouslayer thereon, is also suitable for forming castings in a mold bodyconsisting of loose sand without binder, for instance of free flowingquartz sand.

The incorporation of reactants such as alloying elements in the cellularplastic pattern has the great advantage that, for instance, startingwith a casting charge of regular pig iron, a cast body of alloyed metalcan be produced. The loss of the usually valuable reactants or alloyingmaterials is insignificant and can be further reduced by using theporous heat resistant layer interposed between the cellular plasticpattern and the mold body. When it is desired to influence the hardnessor other qualities of only the surface portion of the casting, then suchreactants are preferably applied as a thin layer or incorand similarmaterials which are known by the trade name Freon. Thereby it will beachieved on the one hand that combustion of the cellular plastic isprevented and consequently the amount of gas which has to be removedupon gasification of the plastic is reduced and, on the other hand, itis possible in this manner to carry out the pouring of the castingcharge in a protective gas atmos phere. It is also possible, accordingto the present invention, to incorporate gaseous halogens such aschlorine in the expanded plastic, i.e., in the cells thereof whichhalogens, particularly chlorine, will react advantageously with certainlight metal melts, such as a casting charge of aluminum. Particularlythe type of heat resistant layers or coatings which become porous onlywhen subjected to heat, will permit the storing of the cellular plasticpatterns covered with such heat resistant layer for a considerablelength of time, without loss of the gas incorporated in the plasticpattern.

In general, cores are not required in connection with patterns made ofgasifiable expanded plastic material. If, however, in exceptional casessuch cores are required due to poor accessibility of interior recessesof the plastic pattern, then the cores may be incorporated when foamingthe expanded plastic patterns or they may be inserted thereafter. Forthis purpose it is possible to use not only cores made of conventionalmaterial, i.e., bonded sand and the like, but also cores which consistof gasifiable expanded plastic, provided that the gasifiable expandedplastic core is surrounded by a solid layer of low thermal conductivity,a so-called heat barrier layer, which will retard the transmission ofheat from the melt to the expanded plastic core until after the meltlayer adjacent the core, i.e., outwardly and adjacent of the solid layerof low heat conductivity, has solidified. Due to the high temperature ofthe casting charge, the core will then be gasified and a recess willremain in the casting, the latter being covered adjacent to such recessby the barrier layer which can be easily blown off or otherwise removed.

Such barrier layer may consist of gypsum, clay, magnesium, calcium oxideor similar materials with hydraulic or organic binders such as polyvinylacetate resin, starch and the like, or including metal powders or metalflakes, and the heat barrier layer may be applied to the expandingplastic core in the same manner as the heat resistant porous coating isapplied to the expanded plastic pattern. Usually, a thickness of thebarrier layer of a few millimeters will be sutficient for retarding heattransmission therethrough to such an extent that the core will begasified only after the portion of the charge adjacent to the barrierlayer has solidified.

It is possible to make not only the casting pattern of gasifiableexpanded plastic, but also the pattern for ingate, ventilation andconnecting conduits and/or feeder heads (so-called blind risers), and toadhesively adhere the expanded plastic pattern to the expanded plasticmaterial of such conduits or feeders, either during the foaming processor thereafter. The term feeder is to be understood to denote additionalstorage space for the melt in the mold, i.e., additional space which canbe filled with molten charge. Such an additional space is frequentlydesirable in order to prevent hole or piping formation in metals whichhave a great tendency to shrink.

Hitherto parts of the molding system being particularly susceptible toshrink hole formation were provided with heating means or heatinsulating means by introducing suitable materials into the mold cavityafter having removed a conventional pattern. Thermite mixtures were usedas heating means and hard burne-d ceramical materials which werebrittle, rather expensive and of relatively limited effect served asinsulating material. The coating provided according to the inventionrepresents a considerable progress in this respect, as it can be appliedwithout difiiculty near or at all critical points of the pattern in anydesired thickness in order to secure the insulating effect required inevery particular case. The thickness of the coating may amount to 20 mm.or more. If required, the insulating effect can be increased byconventional heating means. The insulating portions of the coating mayconsist substantially of the above mentioned mineral fiber materials,i.e., asbestos or synthetic mineral fibers. Coatings of this kind haveby far better insulating effects than the hollow ceramic bodiesconventionally used for this purpose. In spite of the relatively loosestructure of such fibrous materials no difficulties arise when embeddingthe pattern, as all forces or stresses occurring thereby are absorbed bythe expanded plastic pattern. The gasifiable patterns are not onlysuited for molding metals but also for molding other melts, as forexample glass and silicate melts and the like provided that theircasting temperature is sufficiently higher than the decompositiontemperature of the expanded plastic material. 1

As an example only without, however, limiting the invention the solidcontent of the intermediate coatings 4 only comprise in percent ofweight: 75-95 pulverized silica, 5-8 ground graphite, 1-5 water glass,up to 3 bentonite, and A1 0,, at the balance.

Referring new again to the drawing, and particularly to the features andembodiments of the present invention illustrated in FIGS. 6-10, it willbe understood that, according to the present invention, spherical feederpatterns are provided which consist of gasifiable material of the typedescribed further above, for instance of a cellular plastic materialwhich will be gasified at the temperature of the molten casting metal.It is essential, according to the present invention, that the feederheads are of substantially spherical configuration and consistessentially of such gasifiable material. Thereby, the difiiculties anddisadvantages are overcome which were encountered when it was attemptedto provide spherical feeder heads by incorporating a hollow sphere inthe molding material. Such hollow spheres are more difficult to produceand must be treated with great care and thereby the advantages ofspherical feeder heads as compared with feeder heads of otherconfigurations are somewhat counterbalanced. Feeder heads of sphericalconfiguration are more suitable than feeder heads of other shapesbecause of the more favorable relationship between volume and surface ofthe feeder head.

The disadvantages connected with the prior art feeder heads areeliminated according to the present invention by providing a feeder headpattern which consists essentially of a gasifiable material, forinstance of expanded plastics, and has a substantially spherical shape.Such spherical feeder head pattern can be suitably arranged, forinstance, in the down gate or runner itself and also directly adjacentto the casting pattern. Thereby it is possible to impart to the feederhead pattern in a simple and technically easily attainable manner themost favorable shape with respect to heat flow and with regard to theratio between volume and surface of the feeder head.

In order to achieve a further reduction of heat losses, the sphericalgasifiable feeder head pattern may be covered with an essentiallyincombustible heat-insulating layer. This layer should be such as toresist erosion and should consist of a material which is either porousor which will become gas-permeable when exposed to the heat of themolten casting metal. Preferably, the heat insulating layer will consistof mineral fibers which are mixed with a hardenable binding agent,substantially as described further above with respect to the gasifiablebodies forming the casting pattern of the present invention. Thethickness of the heat insulating layer surrounding the gasifiable feederhead pattern preferably will be less than 3 mm. It is also possible andwithin the scope of the present invention to cover the gasifiable feederhead patterns with a layer of an exothermic substance, in which case thelayer may he of considerably greater thickness than 3 mm. Suchexothermic heating arrangements, i.e., feeder and riser arrangementswhich are surrounded by heating means which provide heat, for instanceby an alumino-thermic or the like process, are, per se, known to thoseskilled in the art, however, it is now proposed to utilize suchalumino-thermic or the like heating processes or exothermic layers incombination with gasifiable casting patterns and spherical andgasifiable feeder heads.

It is also proposed according to the present invention to incorporatealloying and/or other metallurgically effective substances eitheruniformly or non-uniformly in the feeder head pattern. For instance, byarranging the runner or downgate centrally relative to the feeder head,the substances intended for incorporation in the casting may be embeddedin the feeder head pattern spaced from the 'center portion thereof oreven in the: outer non-gasifiable layer which surrounds the feeder head.This is desirable because alloying substances or the like, if located inthe center portion of the feeder head would be swept awayinstantaneously by and with the penetrating melt.

In such cases where the runner is placed sideways, in

other words extends in a more or less horizontal direction towards thefeeder head and at its other end connects with a downgate, the processis more or less similar, provided however, that the alloy and/ orexothermic substances are, for instance, foamed into the top or outerlayer of the feeder head pattern or, if they are embedded, are locatedin appropriately arranged cavities of the feeder head pattern, namely sothat the alloying or other treating substances will not beinstantaneously swept into the casting pattern by the first portion ofmolten metal entering the feeder head. It is possible by this method toachieve a controlled mixing of the molten casting metal with thealloying constituents. It may be mentioned here that the positioning andthe amount of alloying or other substances which are to be incorporatedin the feeder head pattern will of course vary depending on the size andshape of the casting which is to be produced.

Preferably, the feeder head will be formed with a passage therethroughwhich substantially will be a continuation of the passage formed by therunner through which molten metal is introduced to the feeder head.Provision of such a passage is imp-ortant'in many cases in which it isdesirable that as little as possible of the carbon formed upongasification of the feeder head will enter into the casting pattern ormold cavity in which the cast body is to be formed. By arranging thepassage through the feeder head as described above, the: gasifiedplastic material of the feeder head or at least the major portionthereof will penetrate outwardly through the gas permeable layersurrounding the feeder head and thus will not be introduced into themold cavity in which the cast body is to be formed.

It is also possible to utilize the feeder head pattern of the presentinvention in combination with conventional casting arrangements andprocedures using solid patterns for forming the casting cavity in themold. Preferably, in such cases, at least the patterns for the runner ordowngate will be gasifiable.

According to a further feature of the invention, when using lateralrunners extending more or less horizontally toward the casting pattern,the feeder head may be arranged at the point where the vertical downgatebends to form the lateral runner. In this manner, a more favorable spaceutilization within the mold arrangement is achieved. It is also possibleand frequently advantageous to form the gasifiable feeder head andrunner patterns integral with each other from one piece of expandedplastic material whereby, preferably, the runner should be shaped, inaccordance with aerodynamic prin ciples, so as to prevent the aspirationof air by the stream of molten metal flowing towards the feeder head. Itis also possible to provide in the spherical gasifiable feeder headpattern of the present invention, in a manner known per se, agas-permeable core which, preferably, will be arranged in the uppermostportion of the feeder head pattern or extend downwardly from theuppermost por tion of the same.

Furthermore, it is possible to arrange in the inlet and/or outletpassages, or the patterns for such passages, i.e., either upstream ordownstream of the spherical feeder head, a conventional strainer core.If the feeder head pattern is arranged within the downgate pattern, thensuch strainer core may be placed either upwardly or downwardly of thefeeder head pattern.

The combination of runners and spherical feeder heads is particularlysuitable for the casting of ingots, because it is possible in this caseto save material by surrounding the gasifiable feeder head pattern withexothermic material.

Referring now to FIG. 6 of the drawing, molding box 71 is shown withmold 72 therein corresponding to the shape of the object to be cast.Feeder head pattern 73 is connected with runner 74, as well as withcasting pattern 72 and therethrough connects with riser 75. Feeder headpattern 73, as Well as runner 74, casting pattern 72 and riser 75, areformed of gasifiable material, i.e., material Which will be gasified atthe temperature of the molten metal poured into to the mold for formingthe casting.

In accordance with the present invention, feeder head pattern 73 is ofsubstantially spherical shape and may be arranged in downgate 74directly adjacent to casting pattern 72. The patterns 72, 74 and 75 neednot necessarily consist of gasifiable material, but may also be formedof conventional material such as wood, in which case the patterns 72, 74and 75 must be removed before casting. However, it is essentialaccording to the presently described embodiment of the invention thatfeeder head pattern 3 consists of gasifiable material.

Feeder head pattern 73 may be covered by a heat-insulating layer 73aand/or by an exothermic substance. A core 73b, permeable to gas, mayextend into the interior of the feeder head pattern 73, in a mannerknown per se. The connecting pattern 73c between feeder head 73 andcasting pattern 72 is formed, preferably as illustrated in FIG. 7,namely by arranging the spherical feeder head 73 closely adjacent tocasting pattern 72. Furthermore, as illustrated, feeder head pattern 73is located in the bend 73d formed at the lower end of downgate 74 and,in this manner, the supply conduit for the molten metal becomes shortedand a better space economy is obtained.

As illustrated in FIG. 8, a concentric runner 74 is provided and thefeeder head pattern may consist of one or more portions '73 and 73"which may be provided with relatively large concentric, eccentric or, asshown, decentric grooves 73e into which, for instance, alloying or othermetallurgically effective substances may be introduced. The lower partof the feeder head pattern may be provided with annular recesses 73a asshown in the drawing, which may receive and hold at least one alignedprotrusion 73] of the upper portion 73 of the feeder head pattern. It ispossible to incorporate alloying materials uniformly or non-uniformlyinto and throughout the body of the feeder head pattern, or todistribute these materials only about the surface of the feeder headpattern. Preferably, the feeder head pattern has a hollow core or atleast one passage 73g extending throughout the feeder head in thedirection of flow of the molten metal. It is sometimes also preferred toutilize feeder head patterns according to the present invention to formspherical blind riser patterns 75' which simultaneously serve as feederheads.

According to FIG. 9, the combined runner feeder head pattern 73 includesstrainer core 76 which in the illustrated embodiment is located upstreamof feeder head pattern 73. However, as discussed further above, strainercore 76 or the like may also be arranged downstream of feeder headpattern 73.

The fragmentary view of FIG. 10 will serve to illustrate theadvantageous arrangement of a spherical gasifiable feeder head accordingto the present invention in connection with an ingot castingarrangement. Great economy is achieved in such case if the feeder orfeeder heads 73 are at least partly surrounded with heat insulating orexothermic materials. As shown in FIG. 10, feeder head 73 or at leastthe portion thereof closest to the mold cavity 78 should be surroundedby insulating materials to retard cooling of the molten metal passingthrough these portions of the feeder head. As illustrated, feeder headpattern 73 may be embedded in a separate mold head block 77, or in theupper portion of the proper ingot boxes. The ingot is poured throughfeeder head 73 into the cavity 78 which is surrounded by moldingmaterial 79.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofmolding arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in aningot mold arrangement, it is not intended to be limited to the detailsshown, since various modifications and structural changes may be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalance of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a casting arrangement, in combination,

a member gasifiable substantially without residue on subjection to amolten casting charge and having substantially the configuration of anarticle to be cast, and

a layer of refractory material present in a significant amount up to aquarter inch applied to the outer surface of said member and dries to asolid condition, said layer being solid and gas permeable at thetemperature of the molten casing charge and said member with said layerapplied thereto being embedded in a molding material, whereby saidmember will be gasified upon subjection to the molten casting charge.

2. In a casting arrangement, in combination,

a member gasifiable substantially without residue on subjection to amolten casting charge and having substantially the configuration of anarticle to be cast, a substance distributed throughout said gasifiablemember in significant amounts up to 500% by weight of the member toproduce a predetermined characteristic in said molten casting charge toproduce a predetermined characteristic in said molten casting charge,and

a layer of refractory material which is applied to the outer surface ofsaid member and dries to a solid condition, said layer being solid andgas permeable at the temperature of the molten casting charge, and saidmember with said layer applied thereto being embedded in a moldingmaterial, whereby said member is gasified upon subjection to the moltencasta member gasifiable substantially without residue upon 4.comprising, in combination,

subjection to a molten casting charge and having substantially theconfiguration of an article to be cast, an alloying substancedistributed throughout said member in significant amounts up to 500% byWeight of the member to produce a predetermined characteristic in themolten casting charge, and

layer of refractory material which is applied to the outer surface ofsaid member and dries to a solid condition and has incorporated thereina substance in significant amount up to by weight of the refractorymaterial to produce a predetermined characteristic in the surfaceproperties of the casting, said member with said layer applied theretobeing embedded in a molding material, whereby said member is gasifiedupon a subjection to the molten casting charge and the alloying materialis added to the molten casting charge as it gasifies the pattern and thesurface properties of the casting are improved by the substance in thelayer of refractory material.

For use in a casting member gasifiable substantially without residue onsubjection to a molten casting charge and having substantially theconfiguration of an article to be cast, and

a significant layer of refractory material applied to the 5. comprising,in combination,

outer surface of said member up to a thickness of one quarter inch whichdries to a solid condition, said layer being solid and gas permeable atthe elevated temperature of the molten casting charge whereby saidmember and layer can be wholly embedded in a molding material and themember replaced by the molten casting charge.

For use in a casting arrangement, a casting pattern member gasifiablesubstantially without residue on subjection to a molten casting chargeand having substantially the configuration of an article to be cast, and

a material distributed throughout said gasifiable body 6. comprising, incombination,

in significant amounts up to 500% by weight of the pattern to produce apredetermined characteristic in the casting.

For use in a casting arrangement, a casting pattern member gasifiablesubstantially without residue on subjection to a molten casting chargeand having substantially the configuration of an article to be cast,said member having distributed therethrough a material in significantamounts up to 500% by Weight of the pattern to produce a predeterminedcharacteristic in said molten casting charge, and

a layer of refractory material which is applied to the outer surface ofsaid member and dries to a solid condition and remains solid and gaspermeable at the temperature of the molten casting charge.

arrangement, a casting pattern For use in a casting arrangement. acasting pattern comprising in combination,

member gasifiable substantially without residue on subjection to amolten casting charge and having substantially the configuration of anarticle to be cast, said member having distributed therethrough asubstance in significant amounts up to 500% by weight of the pattern toproduce a predetermined characteristic in the casting, and

a layer of refractory material which is applied to the outer surface ofsaid member in a slurry form and dries to a solid condition, said layerhaving incorporated therein a substance in significant amounts up to 10%by weight of the refractory material to produce a predeterminedcharacteristic in the surface properties of the cast article whencontacted by the molten casting charge.

In a casting arrangement, in combination,

a casting pattern consisting essentially of a member gasifiablesubstantially without residue on subjection to a molten casting chargeand having substantially the configuration of an article to be cast,

a blind riser pattern of substantially spherical configuration andconsisting essentially of a material gasifiable substantially withoutresidue on subjection to a molten casting charge and being operativelycon nected to said casting pattern, said pattern having a conicalindentation in its upper surface extending downwardly into said pattern,

and a body of gas permeable molding material enveloping and havingembedded therein said casting pattern and said substantially sphericalgasifiable feeder head pattern with said molding material filling theindentation in said blind riser pattern to provide a gas permeable,solid material which remains solid at said elevated temperature andprojects downwardly into said substantially spherical blind riserpattern.

References Cited by the Examiner UNITED STATES PATENTS T. SPENCEROVERHOLSER, Primary Examiner. MICHAEL V. BRINDISI, MARCUS U. LYONS,

Examiners.

E. MAR, Assistant Examiner.

5. FOR USE IN A CASTING ARRANGEMENT, A CASTING PATTERN COMPRISING, INCOMBINATION, A MEMBER GASIFIABLE SUBSTANTIALLY WITHOUT RESIDUE ONSUBJECTION TO A MOLTEN CASTING CHARGE AND HAVING SUBSTANTIALLY THECONFIGURATION OF AN ARTICLE TO BE CAST, AND A MATERIAL DISTRIBUTEDTHROUGHOUT SAID GASIFIABLE BODY IN SIGNIFICANT AMOUNTS UP TO 500% BYWEIGHT OF THE PATTERN TO PRODUCE A PREDETERMINED CHARACTERISTIC IN THECASTING.